Why Use a Gill Ultrasonic Anemometer?
Ultrasonic technology relies on the measurement of sound waves between fixed transducers. A typical Gill two-axis anemometer measures the times taken for an ultrasonic pulse of sound to travel from the North transducer to the South transducer, and compares it with the time for a pulse to travel from S to N transducer. Likewise times are compared between West and East, and E and W transducer. If for example, a North wind is blowing, then the time taken for the pulse to travel from N to S will be faster than from S to N, whereas the W to E, and E to W times will be the same. The wind speed and direction can then be calculated from the differences in the times of flight on each axis. This calculation is independent of factors such as temperature. Some Gill ultrasonic anemometers also provide Speed of Sound and Sonic temperature outputs, these parameters are important in some research applications.
Another important factor in the use of the ultrasonic technique is that the instruments can provide inherent diagnostic capability. With a mechanical anemometer you do not know if it is not working or if there is no wind if zero wind is reported. With Gill ultrasonic anemometers you can provide a health check as part of the output stream.
Gill ultrasonic anemometers are no longer expensive instruments. The Gill entry-level anemometer the WindSonic is comparable in price to professional quality cup and vane /propeller units, and ultrasonic anemometers are rapidly becoming the instrument of choice for all professional measurements.
Gill ultrasonic anemometers, unlike mechanical units, do not require routine maintenance. Mechanical units will need bearing replacement through life, which will mean sending the instrument away for service, this is expensive and will mean a loss of data for a period. If you add the cost of this maintenance to the initial purchase price this will provide a true through life cost. When comparing this through life cost you will find that comparable performance Ultrasonic anemometers have a lower through life cost than mechanical units. This has been verified by independent studies.